Between that was a 1-1 draw, Jesse Lingard opening the scoring on the stroke of half-time at Levi's Stadium thanks to a mesmerising assist from Anthony Martial before Casemiro levelled from the spot after Victor Lindelof fouled Theo Hernandez with a dreadful tackle inside the area.
The sides will meet again on Tuesday August 8 in the UEFA Super Cup in Macedonia, with United priced up by Sky Bet as 3/1 outsiders and Real favourites at 5/6 (draw 5/2).
Martial faltered under Mourinho last season and has been linked with an Old Trafford exit as the Reds move for Inter Milan winger Ivan Perisic.
That deal is proving hard to get over the line but in Martial they have a fine player on the left flank. The 21-year-old Frenchman's ballooned spot-kick should not blemish a display in which his remarkable feet and pass for Lingard underlined his superb potential.
Mourinho will have winced when influential Ander Herrera went off injured and at some of his players' penalties on an afternoon that ended as amusingly as it began.
Rapper Drake brought out the match ball at the Manchester derby in Houston and this time the face of McDonald's did the honours.
Modern football peaked as Ronald led the bemused players out and shook all their hands before a match that felt anti-climactic after the pre-match hilarity.
Aside from an early Lingard strike, there was little to report before the players went off for a drinks break after 30 minutes.
Andreas Pereira, back from a loan spell at Granada, looked bright in United's midfield and Madrid's star-studded attack showed glimpses of their quality, yet there were few moments of note until the final five minutes of the first half.
Phil Jones reacted well to prevented a Gareth Bale cross finding Karim Benzema and Eric Bailly swept up a Luka Modric cross after Lingard curled wide at the other end.
The England international, so impressive on this tour, would soon open the scoring, but it was Martial he had to thank.
Incredible footwork allowed him to wriggle between Modric and Dani Carvajal before smartly directing into the path of Lingard to sweep home.
United made eight changes for the second half, but half-time introduction Herrera did not last long after being hurt in a challenge.
Scott McTominay came on as Mourinho spoke to the officials, with play continuing in a similarly disjointed manner to the opening period as Marouane Fellaini headed over.
Madrid were only threatening sporadically but drew level in the 69th minute as summer signing Lindelof rashly brought down Theo Hernandez. Casemiro stepped up and rifled past David De Gea.
The Spain goalkeeper, ruled out of a summer move to the Bernabeu, did brilliantly to claw away a cheeky free-kick from Luis Miguel Quezada, before Fellaini wasted a fine chance from McTominay's cross.
Dani Gomez dragged wide before the match went to penalties, with Martial ballooning well over only to see Matteo Kovacic denied by De Gea.
McTominay and Oscar were then thwarted, before Henrikh Mkhitaryan and Quezada finally found the net.
Lindelof's terrible penalty was comfortably stopped before Hernandez dragged wide, with Daley Blind scoring before Casemiro hit the crossbar to give United victory.
